The effect of alpha and beta adrenergic stimulation and blockade on uteroplacental hemodynamics in pregnant sheep before and after the production of renal hypertension will be studied. Dose-response curves to agonists will be determined for both systemic (jugular vein) and local administration (uterine artery). The response of the uteroplacental circulation to both alpha and beta adrenergic blockade will also be determined before and after hypertension. In addition, the effects of selective beta blockade will also be tested. We will also be utilizing a model of chemical sympathectimized pregnant sheep to further elucidate the role of the autonomic nervous system in one-kidney renal hypertension.